If you guys google 'Reipatcher Unity' then the first result is a github with detailed install instructions.
You must be registered to see the links
go here, scroll down to Installation -> Standalone Installation (ReiPatcher) then follow the instructions. It is very easy to install, especially if you follow the instructions.
Also take note it does MTL via the internet so you both need an internet connection and you might need to wait a sec for the text to be translated.
Yes I support JP game creators through ci-en using dlsite points. I login to JP DLsite and use my Aussie credit card to buy points, then I use those points on ci-en.
The prices are, of course, in JP Yen so convert Yen to your local currency to get a rough idea. (1 point = 1 yen, minimum purchase 1000 points ~= $13 AUD for me, for example)
It is monthly, works exactly the same as Patreon. EDIT = The same as Patreon as in, if you cancel your sub early you get the rest of the month anyway but it doesn't auto-renew.
Yes you need to have a JP DLsite account.
I cannot recommend one over the others as I have only used ci-en, but it's been nothing but a pleasant experience for me and I can't read Japanese, I just use google page translate.